Rotifer Tips and Tricks... The secrets to a successful rotifer culture
Rotifer Tips and Tricks….The secrets to a successful rotifer culture
Aquaculture is heavily reliant on live rotifer feeds for the larval rearing of many marine and some freshwater fish. Sustainable Nutrition recommends using rotifers as a first feed for zebrafish fry with small mouth size. In any hatchery operation, the main objective is to provide healthy, nutritionally enriched rotifers on demand. This is more important than the marginal cost reduction that would be achieved growing compromised rotifers at very high densities.
Did you know? Rotifer cultures are quite sensitive to water quality. If rotifers are suffering from poor water quality in their culture, they are stressed and stop eating. Feeding fish larvae starving rotifers does not supply them with the nutrients necessary for robust growth. Additionally, as a rotifer density surpasses 500 per ml, the rotifer culture accumulates metabolites and water quality declines. Eventually, once a rotifer culture reaches a density of 1000 to 2000 per ml, it becomes prone to periodic crashes! After years of struggling with culturing rotifers at high density in open systems, our pilot customer, Sustainable Aquatics Inc converted to a closed, batch culture system which has been very consistent, with no crashes. They converted to our culture system using closed bags, a sub-micron filtered water and air, and clean algae and rotifer cysts for inoculation.
Let’s talk about algae! We also believe that the best, most consistent results are obtained when rotifers are cultured on a diet of live algae. We suggest the motile green alga Tetraselmis suecica: https://snextracts.com/collections/for-rotifers-and-artemia/products/sterile-tetraselmis-algae. It grows very well in low salinity, high density cultures and resists invasion by other unwanted algae species.
But…don’t forget about the salinity of your water! We recommend culturing your rotifers at 6ppt, and enriching at 2ppt, in order to minimize osmotic shock when you transfer the rotifers to feed larval fish.
Which rotifer is for you? The mouth gape sizes of larval fish determine the size of rotifer prey that can be ingested, so it is important to provide an appropriately sized rotifer to facilitate successful larval rearing [1]. We stock more than a dozen brachionid species, ranging in size from 120 to 300 µm in length, each with different physiological optima. [3].
Proales similis is one of the smallest rotifer species measured, averaging only 88µm in length, and inhabit low salinity waters. With 63 species documented, most of which occupy freshwater, Brachionus is the oldest known genus among the monogonont class of rotifer [3]. B. rotundiformis are the smallest of the brachionid species, measuring approximately 120 µm long, and prefer higher salinities and temperatures. B. manjavacas and B. plicatilis are larger, averaging approximately 247µm and 261µm in length, respectively. B. plicatilis also grow better at lower salinities and temperatures than other brachionid species, and inhabit inland salt lakes and coastal marine habitats [1,3]. One additional way to optimize rotifer production and culture stability is to select among the brachionid species best suited for growth under the specific environmental conditions of the hatchery, and also those that are best suited for the specific geographic region of the world [1].
Moreover, using an appropriate size rotifer for larviculture largely contributes to its overall success. A 2007 study reported that 15 days post-hatch larval grunt Parapristipoma trilineatum fed B. rotundiformis grew much better for the first 7 days than larvae fed B. plicatilis, exclusively. However, after day 7 the same larvae grew better when fed the larger B. plicatilis [2]. Maintaining mass cultures of two different size rotifers may benefit hatcheries by increasing the overall success of larviculture.
What happens if your rotifer culture crashes? For this reason, we suggest always keeping a backup of rotifer cysts in case of emergencies. Rotifer cysts can be hatched in 24 hours into thousands of young rotifers capable of rapid asexual reproduction to inoculate mass cultures. We offer types of L-strain, including Brachionus plicatilis and B. manjavacas, and multiple types of S-strain Brachionus rotundiformis. For those that love to experiment, we even offer a sample pack of 15 different rotifer strains that you can use to optimize rotifer prey to your larval predator.
Rotifer cysts can be found on our website:
We also conveniently offer shipping of enriched live rotifers as one other option, which ship within 1-2 days of ordering: https://snextracts.com/collections/live-amplifeed-enriched-rotifers. Hatcheries often find it difficult to maintain pure-rotifer cultures with no cross-contamination. Periodically re-inoculating a rotifer culture using rotifer cysts, allows hatchery managers to maintain tighter control over the genetic composition of their rotifer species. Sustainable Nutrition’s benchtop rotifer culture system is designed for ease of quickly re-starting cultures genetically characterized rotifers [1].
With that in mind, check out our benchtop rotifer production system! Available in both 30L and 50L sizes, and convenient for a zebrafish or small aquaculture lab. One two-foot system is designed to produce enough rotifers to meet the needs of most small to medium sized labs. It also offers built-in redundancy to minimize the impacts of inopportune rotifer culture crashes: https://snextracts.com/collections/zebrafish/products/complete-benchtop-rotifer-production-system-30l
What is our secret to success? Amplifeed Replete! We have observed a tremendous benefit to enriching rotifers in the last 24-36 hours prior to feeding to fish larvae. Rotifer enrichment significantly enhances the rate of growth, maturation, and survival of larval fish. We observe that optimizing larval nutrition is as important as egg yolk quantity and quality, and is the most important factor in the long-term health and productivity of fish. Formulated with our nano-emulsified astaxanthin, we believe that Amplifeed Replete is the best rotifer enrichment on the market.
We are always happy to offer suggestions, or answer any questions that you may have!
Sincerely,
The Sustainable Nutrition Team
[1] Snell T.W., Johnston R.K., Matthews A.B. Utilizing Brachionus biodiversity in marine finfish larviculture. 2018. Hydrobiologica. 844: 149-162.
[2] Hagiwara A., Suga K., Akazawa A., Kotani T., Sakakura Y. 2007. Development of rotifer strains with useful traits for rearing fish larvae. Aquaculture. 268: 44-52.
[3] Snell T.W., Genetic Resources of Rotifers in the Genus Brachionus. 2019. The Biological Resources of Model Organisms. 55-67.